High-tensile-strength paper-like webs made of synthetic nonwoven composites have diverse application as insulating housewrap, bookbinding and protective wrap materials. For such applications it is advantageous to provide a paper-like material which is printable and characterized by high tear resistance.
A known material suitable for use as a housewrap and other high-strength applications is marketed under the brand designation TYVEK by E. I. Du Pont de Nemours and Company, Wilmington, Del. TYVEK is 100% spunbond polyethylene fiber bonded by heat and pressure. TYVEK style 1042B, which is marketed as a housewrap material, has the following properties: basis weight --26 lb/3000 ft.sup.2 ; thickness--4.9 mils; tensile MD--20 lb/inch; tensile CD--22 lb/inch; tear MD--0.7 lb; tear CD--0.7 lb; opacity--75%; internal bond--0.35 lb/inch.
U.S. Pat. No. 4,162,180 to Burton et al. discloses a flexible wall covering material comprised of pulp and two thermoplastic polymeric fibers having different plasticity temperatures. The polymeric fibers are selected from the group consisting of polyolefins, polyamides, polyesters, polyurethanes, polycarbonates, vinyl and acrylic resins. In wall covering applications, the sheet material is heated to a temperature intermediate the plasticity temperatures of the two thermoplastic materials, so that the fibers of one of the thermoplastic materials are rendered plastic and fuse together to form a three-dimensional network in the sheet while the other thermoplastic material retains its fibrous structure.
Canadian Patent No. 787,649 discloses nonwoven materials made of a mixture of three-dimensionally oriented fibers of different lengths. In accordance with the disclosure of this prior art, synthetic fibers, natural fibers and fibers made of inorganic materials can be used either alone or in a mixture with each other. The synthetic fibers may include polyamides, polyesters, polyacrylonitrile, polyvinyl chloride, polyvinylidene chloride, polyolefins and polyurethanes used alone or in mixture with each other. The Canadian patent discloses that the synthetic fibers can be of different lengths. In particular, in Examples 1 and 7 a nonwoven material is described which includes polyethylene terephthalate fibers of four different staple lengths. Example 4 is directed to a nonwoven material which includes polyethylene terephthalate fibers of six different staple lengths.